Purification of single-wall carbon nanotubes by microfiltration

A purification procedure for single-wall carbon nanotubes (SWNTs) prepared by pulsed laser ablation is discussed, which separates coexisting carbon nanospheres (CNS), metal nanoparticles, polyaromatic carbons, and fullerenes from the SWNT fraction, The process involves the suspension of CNS, metal nanoparticles, and SWNTs in an aqueous solution using a cationic surfactant and the subsequent trapping of SWNTs on a membrane filter, No oxidative treatment is required. Scanning/transmission electron microscopy and Raman scattering were used to evaluate the purification process and the vibrational features of SWNTs. Purity of SWNTs at the final stage sample is in excess of 90% by weight, and no evidence of impurity carbon phases was revealed in the Raman spectrum of the SWNT fraction.